Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Research Article Interference Excision in Spread Spectrum Communications Using Adaptive Positive Time-Frequency Analysis | Hindawi Publishing Corporation EURASIP Journal on Wireless Communications and Networking Volume 2007 Article ID 14916 9 pages doi 2007 14916 Research Article Interference Excision in Spread Spectrum Communications Using Adaptive Positive Time-Frequency Analysis Sridhar Krishnan and Serhat Erkíũcĩũk Department of Electrical and Computer Engineering Ryerson University Toronto ON Canada M5B 2K3 Received 26 July 2006 Revised 10 February 2007 Accepted 24 May 2007 Recommended by Richard Kozick This paper introduces a novel algorithm to excise single and multicomponent chirp-like interferences in direct sequence spread spectrum DSSS communications. The excision algorithm consists of two stages adaptive signal decomposition stage and directional element detection stage based on the Hough-Radon transform HRT . Initially the received spread spectrum signal is decomposed into its time-frequency TF functions using an adaptive signal decomposition algorithm and the resulting TF functions are mapped onto the TF plane. We then use a line detection algorithm based on the HRT that operates on the image of the TF plane and detects energy varying directional elements that satisfy a parametric constraint. Interference is modeled by reconstructing the corresponding TF functions detected by the HRT and subtracted from the received signal. The proposed technique has two main advantages i it localizes the interferences on the TF plane with no cross-terms thus facilitating simple filtering techniques based on thresholding of the TF functions and is an efficient way to excise the interference ii it can be used for the detection of any directional interferences that can be parameterized. Simulation results with synthetic models have shown successful performance with linear and quadratic chirp interferences for single and multicomponent interference cases. The proposed method excises the interference even under very low SNR conditions of -10 dB and the technique could be easily .
